Sung Hoon was a normal High School student, but one day he finds himself with a cute little tiger girl. He is told that the world will end if he doesn't marry her. Thus the story begins with the cute smile of the tiger girl.

The long-told myth of Dangun was true, and Hwanung felt sorry for the sealed tiger and promises one thing. The promise was that when the time for the seal to be broken comes, she must fall in love with her husband-to-be and the tiger will be freed. Gang Seonghun, an ordinary high school student, goes to Jirisan Mountain where his grandfather lives and learns about the history of his family, the "Guardian of Tigers."